Question

In DNA of uniform composition, a specific hexanucleotide occurs by chance once in every 4096 base pairs. The recognition sequence for EcoRI is a hexanucleotide. How many restriction sites for EcoRI would you expect to exist in lambda DNA if the phage DNA were of uniform composition? There are few restriction sites for a number of enzymes including EcoR1 and HpaI in the left 20 kilobase of lambda DNA. Explain. (Hint: The left region of lambda DNA is rich in G+C base pairs.) Can evolution of E. coli and /or the lambda phage explain this discrepancy? Explain. (3 points)